RU2227857C1 - Method for laying pipeline in a swamp - Google Patents

Abstract

FIELD: pipeline construction technology. SUBSTANCE: method includes preparation of traffic way along pipeline placement area, delivery of backfilling soil to pipeline placement area, placement of geotextiles material on the pipeline and swamp surface, covering of geotextiles material with soil, overlapping of backfilling with geotextiles material, connection of geotextiles material edges and covering of geotextiles material perimeters with soil. Geotextiles material are placed with lap portions along length, backfilling is performed in separate portions, interacting along slanting surfaces of natural slants, overlapped by lap portions and longitudinal edges of geotextiles material with following connection of said portions. Backfilling height is dependent on variable swamp depth. Mathematical formula for calculating height is provided. EFFECT: increased pipeline reliability. 4 cl, 4 dwg

Description

The invention relates to the field of construction of gas and oil pipelines in deep swamps with an uneven thickness of the peat layer.

A known method of ballasting and securing the pipeline in a trench when laying it in flooded soils using reinforced concrete weighting agents [1]. The disadvantages of the method are as follows:

- the installation of reinforced concrete weighting agents requires the formation of a trench and drainage at the installation site, which is almost difficult to accomplish with a large length of the swamp;

- design loading causes uneven deepening of the pipeline into flooded peat due to its variable thickness, which contributes to the development of bending moments that reduce the reliability of the pipeline;

- hard and heavy reinforced concrete blocks create local loads on the pipe walls, cause local stresses in it, which also reduce the reliability of operation;

- the use of reinforced concrete weighting compounds is associated with increased material and transport costs, and, as operating practice shows, these costs are not always justified due to the low quality of weighting materials.

As a prototype of the claimed invention, the method of embankment of the pipeline with geotextile shells with soil was selected [2]. According to the prototype, the geotextile canvases are laid out on the pipeline, an embankment is created with mineral soil, the soil is compacted, it is covered with the upper geotextile, the upper fabric is connected to the lower, and the fabric is sprinkled with mineral soil.

The disadvantages of the prototype method are as follows:

- the dimensions of the embankment are not related to the depth of the swamp, and therefore, with uneven peat thickness of the swamp, the sediment of the pipeline with the embankment will also be uneven, which will cause the development of bending moments in the pipeline and a decrease in its reliability during operation;

- the use of the upper and lower canvases forces to make two longitudinal connections, reducing the reliability of the embankment when it is immersed in the swamp and pulling the canvases, in addition, the laying speed decreases when two extended connections are made;

- continuous backfilling of canvases without sectioning them in the form of separate blocks along the length of the pipeline reduces the reliability of ballasting with through damage to the lower canvases, leading to the washing out of the backfill with longitudinal water drains over a considerable length, exposing the pipeline and losing its longitudinal stability.

The objective of the invention: improving the reliability of the pipeline in the swamp by ensuring uniform precipitation and dividing the backfill into separate blocks.

The object of the invention is a method of laying a pipeline in a swamp, including preparation of a long-haul passage, delivery of backfill soil to the place of laying, laying of geotextile carpets on the pipeline and the surface of the swamp, backfilling of geotextile carpets with soil, overlapping of backfill with geotextile carpets, connecting their edges and sprinkling with carpets, so that that geotextile carpets are laid out with overlapping lengths, and backfill is carried out in separate blocks interacting with each other along inclined surfaces of natural slopes of the backfill, overlapping overlapping sections and the longitudinal edges of the geotextile carpets with their subsequent connection with each other, and the backfill height is selected depending on the variable depth of the swamp according to the formula

where h is the height of the backfill, m;

γ _gr - volumetric weight of the soil backfill, N / m ³ ;

γ _t - volumetric weight of peat, N / m ³ ;

γ _sb — volumetric weight of the backfill soil in suspension (in water), N / m ³ ;

H - the depth of the swamp, m;

S _article - stabilized pipeline sediment, m

The objective of the invention is also solved by the fact that the length of the overlap area exceeds the length of the inclined part of the backfill by a value of 1.0 D _n , where D _n is the outer diameter of the pipeline.

The objective of the invention is also solved by the fact that the lower edge of the inclined surface of the backfill does not reach the edge of the carpet by a value of 1.0 D _n .

The objective of the invention is also solved by the fact that as geotextile carpets, non-woven synthetic material webs are used, interconnected, for example, by a gas torch welding method.

Salient features of the claimed invention are the following:

- geotextile carpets are laid out with overlapping sections along the length;

- filling is carried out in separate blocks, interacting with each other along the inclined surfaces of the natural slopes of the filling, overlapping sections of the overlap and the longitudinal edges of the geotextile carpets with their subsequent connection;

- the filling height is selected depending on the variable depth of the swamp according to the formula

where h is the height of the backfill, m;

γ _gr - volumetric weight of the soil backfill, N / m ³ ;

γ _t - volumetric weight of peat, N / m ³ ;

γ _sb — volumetric weight of the backfill soil in suspension (in water), N / m ³ ;

H - the depth of the swamp, m;

S _article - stabilized draft of the pipeline, m;

- the length of the overlap section exceeds the length of the inclined part of the backfill by a value of 1.0 D _n , where D _n is the outer diameter of the pipeline;

- the lower edge of the inclined surface of the backfill does not reach the edge of the carpet by a value of 1.0 D _n ;

- as geotextile carpets webs of non-woven synthetic material are used, interconnected, for example, by welding with a gas torch.

The applicant is unknown from the patent and technical literature the above significant distinguishing features.

These significant distinguishing features allow us to consider the claimed invention to be new.

The claimed invention also meets the criterion of “Inventive step”, because significant distinguishing features in conjunction with the known ones allow to obtain a new effect when laying pipelines in difficult conditions of swamps and at the same time solve the task of ensuring the reliability of the pipeline.

The invention can be successfully applied in the construction or overhaul of pipelines in long deep bogs with uneven thickness of the flooded peat layer, which has a low bearing capacity.

The proposed method allows for more uniform settlement of the pipeline, thereby reducing the level of bending moments along its length during operation, and the mechanism of connecting the end sections of geotextile carpets increases the reliability of sealing the soil backfill in the form of separate blocks against washing out soil particles from the cavity of geotextile carpets and ensures a stable position of the pipeline in a peat environment.

The above allows us to conclude that the invention meets the criterion of “Industrial applicability”.

The essence of the method is shown in figures 1-4. Figure 1 shows a cross section of a pipeline; figure 2 is a side view of the docking node of two adjacent blocks of filling; figure 3 is a sectional view of the docking of adjacent filling blocks; figure 4 is an implemented diagram of the pipeline in the swamp along the profile.

The method is carried out in the following order. Preparing along the highway. At the width of the strip, the plant layer 1 is removed, mineral soil is imported and distributed along the length of the strip. Welded into a continuous thread, the pipeline 2 is laid on the surface 3 of flooded peat 4 (figure 1).

On the pipeline 2, the surface 3 of the swamp and the vegetation layer 1, flexible carpets 5 are laid out with overlap sections 6 rolled up into rolls (FIG. 2).

Excavator make filling the soil in the form of blocks 7, 8 of a trapezoidal section (Fig.1-3) of the estimated height h depending on the depth of the swamp H, equal to the distance from the surface 3 to the mineral bottom 9 (Fig.1). With the formation of the backfill unit 7, an inclined surface 10 is formed due to the angle of repose of the soil 7, the lower edge of which does not reach the edge of the carpet 5 by the amount l _n = D _n , where D _n is the outer diameter of the pipeline (figure 2). Then, the backfill unit 7 is overlapped with the backfill-free portion l _n and the longitudinal edges of the carpets 5 with their subsequent connection between themselves. Until the filling of block 8, the roll 6 is deployed and laid on an inclined surface 10 and on top of the filling block 7 by a value of l _n (Fig.3). The filling of block 8 ends with the alignment of the height of the filling at the junction of the filling blocks 7 and 8.

The free end 6 of the carpet 5 of length l _{n is} imposed on the backfill unit 8, the longitudinal edges of the carpet 5 are wrapped and the superimposed transverse and longitudinal edges are connected to each other. After that, the backfill blocks 7 and 8 are sprinkled with a vegetable layer 11 (Fig. 4).

The final view of the gasket is shown in figure 4. The variable profile of the top of the backfill 12 depends on the profile of the mineral bottom 9 of the swamp, the backfill blocks interact with each other along inclined surfaces 10 through layers of laid carpets made of non-woven synthetic material (HCM). The pipeline 2 is located below level 3 of the surface of the swamp 4. The peat vegetation layer 11 compensates for the insufficient thickness of the backfill layer over the pipeline 2 in the deepest places of the swamp 4.

The invention works as follows. During operation, a variable filling height will provide a stabilized draft S _st (Fig. 1), which will exclude the development of dangerous bending moments in the pipeline body. Backfill, acting like ballast enclosed in sealed NSM shells with reliable sealing of end and longitudinal joints, will ensure a stable position of pipeline 2 against ascent and transverse horizontal displacements due to the fact that shells with soil tightly enclose pipeline 2 and are held on it, creating an artificial foundation . Thus, this method of laying the pipeline 2 in the swamp ensures that the objective of the invention is achieved.

Example.

Overhaul of the pipeline 2.5 km long is carried out overhaul of the pipeline 2 by its complete replacement with new pipes due to unacceptable metal corrosion, destruction of some reinforced concrete weighting agents and the emergence of the gas pipeline. Swamp of type II-III, depth 3-7 m. It is necessary to determine the main parameters of the laying. Initial data: diameter and wall thickness of the pipe 1020 × 10.5 mm, geotextile - non-woven synthetic material (HCM) from nylon fibers of Khimvolokno OJSC, TU 6-00-00204-027-1995 in the form of rolls with a width of 1.85 m; bulk weight of peat - γ _t = 9000 N / m ³ ; volumetric weight of backfill soil in its natural state γ _gr = 16000 N / m ³ , the same in water - γ _sb = 6000 N / m ³ ; angle of natural slope of the soil φ _gr = 40 °. The necessary deepening of the pipeline 2 into the swamp S _st = 1.8 m

First, we determine the geometrical parameters of the backfill depending on the depth of the swamp, using the formula of [3] for stabilized precipitation S _{st of} drained swamps during plastic extrusion of peat due to the weight of the embankment:

In [3], a tabular dependence of the plasticity coefficient of peat K on the depth H of the swamp was also given, which can be expressed analytically with a minimum error

where H has a dimension in meters.

Substituting (2) in (1) and expressing the height of the embankment h, we obtain the dependence

Substituting the initial data in (3), we obtain the dependence of the filling height h on the depth of the swamp N

Formula (4) shows that with increasing depth of the swamp the backfill height decreases with a constant precipitation of the pipeline 2 with backfill. The cross-sectional area F depends on the height of the backfill

where a, b are the dimensions of the shelves and soles of the original form of backfill (figure 1), m

Given the minimum shelf size a = 1.5 m and the slope angle φ, the area F is equal to

Width _w l carpets HCM determined perimeter section backfill circumference of the pipe l and the amount of overlap of the longitudinal edges of the carpet _nach when screwing.

The formula for determining l _W has the form

Substituting in (6) the initial data and _lax = 0.5 m, we obtain the dependence of the value of l _w on the height h in meters

Let us summarize the results of calculating the height h, area F and width l _w according to formulas (4, 6, 8) depending on the depth of the swamp H in the table.

Consider the elements of laying technology. Carpets 5 LFM are formed by cutting rolls into pieces of cloth length equal to l _W , laying out of cloths with an overlap of 0.2 m and welding them into carpets using a gas burner. The length of the carpet l _dl = 25 m is obtained by connecting 15 canvases. HCM carpets are made in basic conditions, brought to the track and laid out, blocking the pipeline 2, welded into a continuous thread and laid in place of the dismantled defective pipeline over the swamp 3 with the removed vegetable layer 1 at the width b of the backfill (Fig. 1). At the left end of each carpet create a spare area 6 of length l _zap = h / sinφ + 2 m. For example, with h = l, 5 m l _zap = l, 5 / sin40 ° + 2 = 4.6 m.

The mineral soil of the backfill is delivered to the track and distributed along the length of the gasket, taking into account the cross-sectional area F of the backfill (Table 1). The entire volume of soil V _gr backfill depends on the real profile of the mineral bottom 9 of the swamp 4 and in this example can be determined approximately by the formula

F _min , F _max - the smallest and largest values of the cross-sectional area of the filling according to the table, m ² .

Substituting the data in (9), we obtain

The required total area of carpets NSM F _NSM is determined by the formula

, где k₁ - коэффициент перерасхода НСМ при сварке полотен в ковры;

where k ₁ - coefficient of excessive consumption of NSM when welding cloths in carpets;

k ₂ - coefficient of overspending of NSM when laying carpets along the length of the pipeline;

l _W. average - the average value of the width of the carpets, m

The numerical values of the coefficients k ₁ , k ₂ are k ₁ = l, 85 / (l, 85-0.2) = 1.12; k ₂ = 25 / (25-4.6) = l, 23. The average width of the carpet l _{W. average} = 0.5 · (18.8 + 13.7) = 16.3 (table). Substituting the data in the formula (10), we obtain

F _ncm = 1.12 · 1.23 · 16.3 · 2500 = 5.61 · 10 ⁴ m ² .

After backfilling of the NSM carpets 5, welding of the transverse and longitudinal edges, the backfill of the backfill 7, 8 is bonded with the vegetable layer 11. Moreover, the smaller the backfill height h, the greater the thickness of the backfill with the vegetable layer.

The claimed method of laying in comparison with the prototype ensures the stability of the pipeline, reduces bending stresses in the walls of the pipe, resulting in increased reliability of the pipeline in a deep swamp with a variable profile of the mineral bottom, and also does not require special equipment, scarce materials, is easily carried out during construction and overhaul.

Claims (4)

1. A method of laying a pipeline in a swamp, including preparation of a long-distance passage, delivery of backfill soil to the place of laying, laying out of geotextile carpets on the pipeline and the surface of a swamp, backfilling of geotextile carpets with soil, overlapping of backfill with geotextile carpets, connection of edges and dusting of carpets with soil, characterized in that geotextile carpets are laid out with overlapping sections along the length, and backfill is carried out in separate blocks interacting with each other along the inclined surfaces of the natural slopes of the backfill ki, overlapping overlapping areas and longitudinal edges of geotextile carpets with their subsequent connection with each other, and the height of the backfill is selected depending on the variable depth of the swamp according to the formula

where h is the height of the backfill, m; γ _gr - volumetric weight of the soil backfill, N / m ³ ; γ _t - volumetric weight of peat, N / m ³ ; γ _sb — volumetric weight of the backfill soil in suspension (in water), N / m ³ ; H - the depth of the swamp, m; S _ct - stabilized draft of the pipeline, m 2. The method according to claim 1, characterized in that the length of the overlap section exceeds the length of the inclined part of the backfill by a value of 1.0 D _n , where D _n is the outer diameter of the pipeline. 3. The method according to claim 1 or 2, characterized in that the lower edge of the inclined surface of the backfill does not reach the edge of the carpet by a value of 1.0 D _n . 4. The method according to any one of claims 1 to 3, characterized in that as a geotextile carpets use non-woven synthetic material webs, interconnected, for example, by a gas torch welding method.

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